Method and apparatus for heat treating elongated rotary workpieces



Feb. 16, 1965 WITNESSES R. METHOD AND-APPARATUS FOR HEAT TREATING K. WUERFEL ELONGATED ROTARY WORKPIECES Filed May 31, 1961 Fig. I.

W fiwa INVENTOR Richard K. Wuerfel.

PATENT AGENT United States Patent Ofiice 3,l9,8% Patented Feb. 16, 1965 'HNG The present invention relates to an improved method and apparatus for heat treating an elongated rotary workpiece such as an axle or shaft which is substantially of rough surface such as is characteristic of forgings and which includes a longitudinal portion such as an end whichis used in service for transmission of torque or other function as may suit the ultimate purpose of such portion and which during use is required to be maintained true to the axis of rotation of the axle or shaft with a degree of accuracy within several thousandths of an inch.

It is an object of the present invention to provide a method and apparatus for heat treating substantially the entirety of such an elongated workpiece including its end while maintaining alignment of such end with a degree of accuracy referred to above.

By way of exemplification, the elongated workpiece may be in the form of an automobile or tractor axle having a circumferential surface at one end which has been machined to form splines therein, prior to heat treatment by the present method, and the heat treatment may be for purposes of hardening such axle including its splined end.

it is, therefore, another object of this invention to provide a method and apparatus for hardening an axle including a splined end thereof while restricting distortion of the splined end to within the critical degree of alignment, thus obviating the need for ali nment inspection of such axle following heat treatment, as well as the need for any straightening of the axle with respect to its splined end following such heat treatment.

Gther objects and advantages of the invention will become apparent from the following detailed description, taken in connection with the accompanying drawing in which:

FIG. 1 is a front elevation view, partly in outline and partly in section, of the novel heat treating apparatus for performing the novel heat treating method; and

2 is-an end elevation view of a portion of the heat treating apparatus taken along the line Il1l in FIG. 1.

In accord with the novel method of the present invention, this method as employed for heat treatment of an elongated workpiece such as a flanged automobile or truck axle It having a splined end 2, comprises the step of first machining on the axle 1 an annular shoulder 3 immediately adjacent to and inwardly of the splined end 2. This annular surface 3 will be turned on a machine (not shown) employing cutting or grinding tools which afford a radial accuracy, for example, one thousandth of an inch relative to a true axis 4 of the axle as defined by the usual 60 conical center cavities 5 and 6 formed in its ends for location of such ends on centers.

The next step of the novel method is the locating and holding of such axle on center'at its opposite ends as by introduction of aligned tapered centering pins 8 and 9 into the conical center cavities 5 and 6.

Following this, rotary confining means It) is moved into a confining position a certain radial distance away from the axis 4. Such radial distance preferably being equal to or slightly less than the radial dimension of annular surface 3, to assure that means 16 will initially contact annular surface 3 at this time, for reasons which Will be explained hereinafter. Such rotary confining means If) is then maintained fixed in such confining position by a considerable force of such as one thousand to sixteen hundred pounds, for example.

Following this step, the axle is caused to be rotated and scanned consecutively by heating and quenching means 11, which may be for purposes of surface hardening the axle and its splined end 2 to the required depth. For purposes of hardening a one inch diameter steel axle one-eighth of an inch deep, for example, the heat may be applied inductively by use of a single-turn coil 12 encircling the axle and energized by an alternating current source (not shown) having a frequency of ten thousand cycles per second and a power level of one hundred kilo watts, while the same coil acts as a quench spray head:

It will be understood, however, that certain features of the present invention may be employed to advantage for other heat treating purposes occasioned by use of other frequencies and power levels applied to the coil 12.

During the final stages of traverse of the heating and quenching means 11 away from the flange 7 along the axle 1 toward the splined end 2, the rotary confining means 19 is retracted out of the path of travel of such means 11 to enable same to pass over such splined end.

inally, the tapered center pins 8 and 9 are withdrawn to free the thus heat-treated axle.

By such novel method, the axle 1 is heat treated along its length including its splined end 2 with assurance that such end will remain true to the axis 4 substantially within the accuracy to which surface 3 is machined, sev-' eral thousandths of an inch, for example. This isaccomplished by virtue of the presence of the rotary confining means ll) while in its active position a certain selected fixed distance from the axis 4- and in contact with the annular surface 3 while the axle is being rotated and scanned by the heat and quench means 11. Any stresses tending to cause bending ofthe axle 1 during such scansion by the means 11 will be prevented from distorting the splined end 2 by the means 10 contacting the annular machined surface 3. Any distortion which may result from such application of heat and quench will be distributed along the length of the axle progressively as scansion by the means 11 ensues. An absence of any confining means intermediate the means It) and the opposite or flanged end of the axle appears desirable on shafts shorter than thirty inches. I

In addition to the general features set forth above, the apparatus for performing steps of the novel heat treating method beyond the step of machining the annular shoulder 3, comprises a heavy rigid frame or base 15 of such as cast iron. This frame may weigh as much as two thousand pounds in an apparatus for hardening steel axles of one inch'to three inches in diameter and up to eighty inches in length. The overall length of such a frame will be in the neighborhood of twelve feet.

Precisely and accurately mounted at opposite ends on the extremely rigid frame 15 are the centering pins Sand 6 which are held aligned to within two thousandths of an inch by virtue of therigidity of the frame 15 and close fit of any parts which may be interposed between such centersand the frame, it being appreciated that the showing of the drawing has been simplified in behalf of facilitating an understanding of the invention and that the physical embodiment of the apparatus will include certain refinements Both centering pins 8 and a axle is absorbed by a rotatable fiange-back-up member 32 which clamps the flange 7 of the axle and strongly urges same to assume a position of perpendicularity with respect to the axis 4. Such a flange gripping arrangement is disclosed and described in detail in copending US. patent application, Serial No. 5,143, filed January 28, 1960.

Such grip also serves as a means for rotating the axle 1 during heat treatment. Bearing means 3 interposed between member 32 and the frame 15 provides for accurate location of member 32 with respect to the axis 4, for rotation of such member, and for transmittal to the frame 115 of the thrust forces received by member 32 from the axle flange 7 under influence of the centering pin 8.

The force delivered by the pin 9 against the splined end 2 of the axle l is preferably merely sufficient to maintain the position of such pin within the conical centering cavity 6 in the end of the axle in the presence of forces created by reaction between the confining means 10 and the annular surface 3 during the heat treat method as aforedescribed. It is desirable that the centering pin 9 be sufficiently rigid to resist deflection under influence of the centering means It on the axle surface 3 while resisting bending of the splined end 2 during heat treatment. In the form shown in the drawing, the diameter of pin 9 has been limited to that of the splined end 2 of the afle 1 in order to allow the integral quench coil 12 to pass over such splined end at completion of the heat treat scanning operation.

The centering means 1% FIGS. 1 and 2, preferably cornprises a pair of rollers 36 and 33 which are spaced apart on a rigid yoke member 39 for movement to the aforementioned active position a certain fixed distance away from surface 3 on the axle 1 when being rotated during heat treatment. The yoke 39' carries respective pins 41 on which the rollers 36 and 3%; are rotatably mounted to permit rolling contact with axle surface 3 when in confining contact therewith. The yoke is actuated to and from its active position via such as a pneumatic cylinder device 43 having a piston 44 subject to such as air pressure admitted to a chamber 45 for advancing the yoke 39 and rollers 36 and 38 via a piston rod 46 to the active position shown in FIG. 2 defined by engagement of such piston with an annular shoulder 47 within the cylinder. A return spring 49 provides for return of piston 44 and means 10 to a repose position as shown in FIG. 1 out of thepath of travel of the integral heat and quench coil 12.

In operation of cylinder device 43,'same will be PICSSUI'".

as a worm drive which isin turn mounted for rotation on the frame 15. The coil 12 finds connection with such drive 55 through the medium of'a connecting member 56 which is in screw-threaded engagement with the worm drive. The worm drive 55 may be rotated for scanning movement of the coil 12 along the axle 1 by a motor (not shown) and a gear 58 which may also serve to effect simultaneous turning of the member 32 via a mating gear 59 during the heat treating of the axle 1. A guide beam 60, secured at opposite ends to the frame 15 and disposed parallel to the axis 4, preferably is provided for guiding cooperation with the member 56 via guide rollers 61 to assure accurate alignment of the coil 12 during its axle scanning movement.

The coil 12 is supplied with alternating current of a preferred frequency from an electrical source (not shown) via the usual electrical leads 62, one of which is shown. The coil 12 in integral quench form as shown, will be supplied with cooling liquid via such as a flexible conduit 63' to enable the quench ports 64 to direct a spray of'quenching liquid radially inward and rearward onto the axle l as same is advanced therealong to heat treat same.

From the foregoing it will be apparent that during scansion of the axle 1 by the integral induction heating and quenching coil 12, by virtue of the presence of the constraining means ltl, which is held forcefully in its active position precisely defined with respect to the axis 4 within several thousandths of an inch, by virtue of the precise machining of the surface 3 to within several thousandths ofan inch of the axis of the axle extending between center cavities 5 and 6, and by virtue of the rigidity ofthe centering pin 9, the spline end 2 of the axle ll may be maintained true to the axis 4 within a total indicator reading of three or four thousandths of an inch, in the presence of any stresses created in the axle as a result, for example, of clamping action of the flange 7 created reactively between pin 8 and member 32 and transmittedfrom the flange to the rod portionof the axle, of thermal stresses created during progressive heating and quenching of the axle, of any frozen-in cold straightening stresses'which may be relieved during the application of heat in the pres- Furthermore, it will be apparent that To enable the cylinder device 43 to be relocated longitudinally of the frame 15, such cylinder device is secured to a mounting bracket 65 which spans side walls 66 and 67 of a quench-collecting basin portion of the frame 15. The bracket 65 includes outwardly-extending flanges 68 and 69 which are supported on respective upper machined surfaces 78 and 71 of side Walls 66 and 67 and are secured in place by removable clamping means 72;

To enable the fixed,radial, distortion-restraining position of the rollers as and 38 to be adjusted with respect to the axis 4 for cooperation with machined, deflectionlimiting surfaces 3 of different diameters, the yoke member 39 has a screw-threaded connection with a socket element 75 carried by the upper end of the piston rod 46 of cylinder device 43. By turning movement of piston rod 46 and piston 44, as by insertion of a tool into an opening 76in element 75, while yoke member 39 is prevented from turning, the effective length of such piston rod can be changed. The yoke member 39 is prevented from turning both during such adjustment'as well as during use of the apparatus, by arms 78 which extend therefrom between parallel-arranged guide plates 79 forming part of l the mounting bracket65 and bridging the side walls 66 and 67 of the frame 15.

It will be understood that the invention should not be construed necessarily in conjunction with the specific embodiment illustrated anddescribed herein, except as defined by the following claims.

I claim as my invention:

1. A method of surf-ace hardening a steel axle workpiece which is substantially of rough surface and which includes a longitudinal portion which during use is required to be maintained true to theaxis of rotation of the axle with a high degree of accuracy, such method comprising the steps of machining anannular shoulder on the outer surface of said workpiece adjacent to said portion and concentric to an axis passing through centers. at its opposite ends, and applying a radial constraining force to said annular shoulder while causing a consecutively heated and quenched zone to scan the workpiece longitudinally during rotation of same about an axis Passing through centers at opposite ends of the workpiece and during the holding of such centers aligned with such axis.

2. A method of hardening a forged steel axle having a splined end, comprising the steps, of machining a smoothsurfaced annular shoulderon said axle adjacent to said splined end concentric to an axis passing through a center at each axle end, and applying a radial constraining force to said annular shoulder while causing a consecutively heated and quenched zone to scan the length of the axle during rotation of the axle about the axis of radially-confined centers at its opposite ends.

3. In a method for surface hardening a steel axle having a splined end and a flanged end, the steps of machining an annular shoulder on said axle adjacent to said splined end concentric to an axis passing through a center at each axle end, and applying a radial constraining force to said annular shoulder while causing a consecutively heated and quenched Zone to scan the length of the axle during rotation of the axle about an axis passing centrally through opposite axle ends, While said ends are held centered on said axis, and while holding the flanged end of said axle in an attitude perpendicular to said axis.

4. A method of surface hardening a forged steel axle which. is substantially of rough surface and which includes a non-cylindrical surface portion which during intended use of the axle is required to be maintained true to the axis of rotation with a high degree of accuracy, such method comprising consecutively heating and cooling the outer surface of a longitudinal zone ofthe axle progressively along the axle length while rotating the axle about anaxis passing centrally through its opposite ends, while holding such opposite ends centered on such axis, and while applying a radial constraining force to said axle intermediate its ends exclusively at an annular machined surface immediately adjacent to the aforesaid non-cylindrical surface portion. i

5. Apparatus for heat treatment of an axle having a splined end and an annular machined surface adjacent to and inwardly of such splined end, comprising retractable centering pin means aligned on an axis common to each for centering engagement with opposite ends of said axle, integral heat-and-quench coil means constructed and arranged to scan said axle for consecutive heating and quenching same, means for rotating said axle during scan-v sion by said coil means, and retractable roller means constructed and arrangedfor actuation to afixed position a predeterminedradial distance away from the axis of said centering pin means for rolling contact with the aforesaid annular shoulder to radially constrain said axle intermediate its ends exclusively at such shoulder during scansionby said heat-and-quench coil means.

6. Apparatus for heat treatment of an axle having a splined end and an annular machined surface adjacent to and inwardly of such splined end, comprising retractable centering pin means aligned on an axiscommon to each for centeringengagement with opposite ends of sfaid axle, heating and quenching means constructed and arranged for scansion of said axle, constraintroller means, and fluid pressure actuator means. operable to actuate said constraint roller means to a fixed position a certain distance from the axis of said centering pin means for rolling contact with the aforesaid annular machined surfaceat one side of said axle to cooperate with said centering pin means to radially constrain the splined end of said axle for centering engagement with opposite ends of said axle,

heating and quenching means constructed and arranged for scansion of said axle, a rigid frame on which apparatus cylinder device, piston rod means operatively connected g components are mounted and which includes a quenchcollecting tub portion having parallel side walls extending between said centering pin means at opposite sides of and beneath said axis, a mounting bracket member bridging said side walls and removably secured thereto for disposition in a position beneath the aforesaid annular machined surface of the axle, constraint roller means, a fluid pressure cylinder device secured to said mounting bracket member and having a piston actuable to a fixed position in engagement with a stop means, said piston being turnable within said cylinder device, piston rod means operatively connected to said constraint roller means for movement of same to a position a selected distance from the axis of said centering pin means for rolling contact with the annular machined surface of said axle,

-means associated with said piston rod means constructed and arranged to adjust the eifective length of connection between said piston and said constraint roller means responsivelyto relative turning movement therebetween, and means cooper-able with said mounting bracket memher to prevent turning movement of said constraint roller means. I

8. Apparatus for heat treatment of an axle substantially of rough textured surface but provided with an annular machined surface adjacent to a working portion to be prevented from bending during such heat treatment,

said apparatus comprising retractable centering pin means aligned on an axis common to each for centering engagement with opposite ends of said axle, heating and quenchingmeans constructed and arranged for scansion of said I axle, a rigid frame on which apparatus componentsare mounted and which includes a quench-collecting tub portion having parallel side walls extending between said centering pin means at opposite sides of and beneath said axis, a mounting bracket member bridging said side walls and removably secured thereto for disposition in a position beneath the aforesaid annular machined surface of the axle, constraint'roller means, a fluid pressure cylinder device secured to said mounting bracket member and. I

having a piston actuaole to a fixed position in engagement with astop means, said piston being turnable within said to said constraint roller means for movement of same to a position a selected distance from the axis of said centering pin means for rolling contact with the annular machinedsurface of said axle, means associatedwith said piston rod means constructed and arranged toadjust the effective length of connection between said piston and said constraint roller means responsively to relative turning. movement'therebetween, and means cooperable with said mounting bracket member to prevent turning movement,

of said constraintroller means.

' References Cited by the Examiner UNlTED STATES PATENTS 3/23 Smith 148-131 2,067,436 1/37 Coberly 'f 266-;4

2,254,306 9/41 Mott et a1. 266 4 2,570,883 10/51 Stivin' 148- 131 2,935,433 5/60 ,Pribyl 266-4 DAVID L. RECK, Primary Examiner. MARCUS U. LYONS, Examiner. 

1. A METHOD OF SURFACE HARDENING A STEEL AXLE WORKPIECE WHICH IS SUBSTANTIALLY OF ROUGH SURFACE AND WHICH INCLUDES A LONGITUDINAL PORTION WHICH DURING USE IS REQUIRED TO BE MAINTAINED TRUE TO THE AXIS OF ROTATION OF THE AXLE WITH A HIGH DEGREE OF ACCURACY, SUCH METHOD COMPRISING THE STEPS OF MACHINING AN ANNULAR SHOULDER ON THE OUTER SURFACE OF SAID WORKPIECE ADJACENT TO SAID PORTION AND CONCENTRIC TO AN AXIS PASSING THROUGH CENTERS AT ITS OPPOSITE ENDS, AND APLYING A RADIAL CONSTRAINING FORCE TO SAID ANNULAR SHOULDER WHILE CAUSING A CONSECUTIVELY HEATED AND QUENCHED ZONE TO SCAN THE WORKPIECE LONGITUDINALLY DURING ROTATION OF SAME ABOUT AN AXIS PASSING THROUGH CENTERS AT OPPOSITE ENDS OF THE WORKPIECE AND DURING THE HOLDING OF SUCH CENTERS ALIGNED WITH SUCH AXIS. 